Ring-spinning system for making yarn having a magnetically-elevated ring

ABSTRACT

A ring-spinning system for making yarn characterized in part by the replacement of the ring traveler configuration with only one rotating, floating ring that has an eye on its inner middle surface. This rotating, floating ring with the eye thereon performs the functions previously performed by the ring traveler configuration of twisting the fibers into yarn. The ring is kept suspended in space by the magnetic levitation system of the present invention. The floating ring is elevated by a well-controlled magnetic field generated by two sets of electromagnetic coils and a set of cylindrical rare earth permanent magnets. The floating ring is rotated around its center by the effect of winding the formed yarns over a rotating spindle at the center of the ring. Sensors and a feedback system are used to control the magnetic fields produced by the electromagnetic coils to maintain the ring in its central position.

TECHNICAL FIELD OF THE INVENTION

The present invention is related to manufacturing yarn from fiberstrands and, more particularly, to a ring-spinning system formanufacturing yarn that employs a magnetically-elevated ring.

BACKGROUND OF THE INVENTION

Spinning is the process of forming yarns from fiber strands. Theexisting spinning systems may be divided into two main categories,namely, continuous spinning systems and non-continuous spinning systems.In continuous spinning, the fiber strand fed to the spinning systemfollows a continuous path throughout the entire spinning process fromthe feeding point to the yarn package. Ring spinning and compactspinning are two examples of continuous spinning systems. Continuousspinning systems generally produce high-quality yarn, and a widediversity of yarn styles, but suffer from a low productivity rate. Onthe other hand, non-continuous spinning systems generally have highproduction rates, but produce relatively low-quality yarn.

The main factor that limits the production rate of ring-spinning systemsis the friction between the traveler and the ring. This frictiongenerates heat sufficient to burn the traveler if its speed is increasedover a certain limit. Therefore, either the speed of the system must bekept below a certain limit to prevent damage to the traveler and/or thetraveler will be damaged and will have to be replaced frequently.Various attempts have been made to reduce the friction between thetraveler and the ring. For example, U.S. Pat. Nos. 2,932,152 and3,851,448 disclose ring-spinning systems wherein the ring is supportedin space by either magnetic force or air pressure to prevent the ringfrom contacting the stationary parts of the system.

These two systems use air pressure to stabilize the ring in thetransverse direction in addition to the magnetic repulsion force.Simultaneously using two different types of stabilizing forces tostabilize the ring complicates the ring-spinning system and makes thesystem unsuitable for industrial applications because the stabilizingforces tend to be difficult to control. Moreover, the absence of acontrol system makes such systems uncontrollable in the case of start-upoperation and in the case of yarn breakage. In addition, the powerrequired by such systems to provide the necessary air pressure andmagnetic forces renders them unsuitable for industrial applicationbecause they are economically inefficient.

A need exists for a ring-spinning system in which the speed andproductivity limitations imposed by the traveler are eliminated. A needalso exists for a ring-spinning system that utilizes a suspended ringand that has the ability of stabilizing the suspended ring with a highdegree of precision. A need also exists for a ring-spinning system thatis capable of producing high quality yarn at a high rate of production,and that is economical in terms of power consumption.

SUMMARY OF THE INVENTION

The present invention provides a ring-spinning system characterized inpart by the replacement of the ring traveler configuration with only onerotating, floating ring that has an eye on its inner middle surface.This rotating, floating ring with the eye thereon performs the functionspreviously performed by the ring traveler configuration of twisting thefibers into yarn. The ring is kept suspended in space by the magneticlevitation system of the present invention.

In accordance with the preferred embodiment of the present invention, afloating ring is levitated by a well-controlled magnetic field generatedby two sets of electromagnetic coils and a set of cylindrical rare earthpermanent magnets. The floating ring is rotated around its center by theeffect of winding the formed yarns over a rotating spindle at the centerof the ring. Sensors and a feedback system are used to control themagnetic fields produced by the electromagnetic coils to maintain thering in its central position. The sensors preferably are inductivesensors that detect the displacement of the floating ring off its centeraxis and send information to a controller of the feedback system. Thecontroller outputs signals in response to the received information thatcause the magnetic force generated by the coils to be adjusted, whichcauses the ring to be restored to its central position.

These and other features and advantages of the present invention willbecome apparent from the following description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of the complete mechanical assembly of thepresent invention.

FIG. 2 is a detailed drawing of the stator assembly

FIG. 3 is a sectional view of the complete assembly

FIG. 4 is detailed drawing of the floating ring

FIG. 5 is a detailed drawing of the stator body

FIG. 6 is a detailed drawing of the flux plates

FIG. 7 a and 7 b is a detailed drawing of the return flux plates (outerand inner).

FIG. 8 is a detailed drawing of the support disk in the Z direction.

FIG. 9 is a floating ring touchdown spacer to keep a minimum air gapdistance of 0.25 mm between the floating ring and the flux plates.

FIG. 10 is a counter spacer of the floating ring touchdown spacer.

FIG. 11 is a finite element mesh of the complete invention.

FIG. 12 is a chart of the restoring force versus the current applied tothe 4 X-Coils at 0.25, 0.5 and 0.75 mm gap between the floating ring andthe flux plates in the X direction.

FIG. 13 is a chart of the restoring force in the Z direction versus thedisplacement of the floating ring in the Z direction and concentric withthe stator body.

FIG. 14 block diagram of the control system of the present invention

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

In accordance with the present invention, a magnetic ring-spinningdevice is provided that is capable of supporting a rotating ring in astable manner around its center without touching the stator part. Arotating spinning ring has an eye that performs the functions equivalentto those performed by the traveler in a conventional ring-spinningsystem. The ring having the eye will be referred to herein as the“floating ring”. This floating ring 3 preferably has a form of a shortcylinder with two flanges at its ends. The floating ring may be madefrom many materials, but preferably is made of a silicon steel materialin accordance with the preferred embodiment of the present invention.

The components of the ring-spinning system in accordance with thepreferred embodiment are shown in FIG. 1. The system comprises a stator1 that has axial holes formed therein for receiving thecylindrical-shaped rare earth permanent magnets 2. The stator 1 alsopreferably has two radially-extending holes 1 b (FIG. 2) foraccommodating two respective displacement sensors 20 (FIG. 2), whichpreferably are of the inductive type. The stator body 1 in accordancewith the preferred embodiment is shown in FIG. 5.

Two sets of flux plates 4 provide return flux paths for the system. Thedesign of one of the flux plates 4 is shown in FIG. 6. The system issymmetric with respect to its components. The left side of the system inFIG. 1 is shown assembled whereas the right side is shown disassembled.Therefore, only the disassembled components will be described. Each fluxplate 4 preferably has five blind holes on one side and one blind holeon the other side. The five holes are made for insertion of the ends ofthe permanent magnets 2 and the other hole is made for insertion of theend of the electromagnet core. These plates 4 preferably are made ofsilicon steel material. Eight electromagnet coils 11 are included in thesystem. Only four of the coils 11 are shown in the disassembled portionof FIG. 1. The coils 11 preferably have silicon steel cylindrical cores.These coils 11 are arranged in two sets. One set is located on one sideof the stator and the other set on the other side in symmetrical way.

Two sets of return flux path plates 12 and 13 are incorporated into thesystem. Each set includes two separate semicircular pieces. Each piececonnects two coils from one side of the system, which will be referredto hereinafter as X-coils or Y-coils. These return flux path plates 12and 13 preferably are made of silicon steel material. The preferreddesign of the flux plates is shown in FIGS. 7A and 7B. A passivesupporting bearing subassembly 7, 8, 10 and 14 (FIG. 1) provides supportfor the axial positioning of the rotating floating ring 3. Thissubassembly includes two annular disks having annular grooves where ringpermanent magnets are installed. One of the annular disks 14 is mountedon the floating ring 3 and has a groove formed in it in which one of thering permanent magnets 11 is installed. The other annular disk in whichthe other ring permanent magnet 8 is installed is mounted on stationarysupport part 7. The stationary support part in accordance with thepreferred embodiment is shown in FIG. 8. The preferred designs for thefloating ring spacer 6 and the stator spacer 5 are shown in FIGS. 9 and10, respectively.

The ring permanent magnets 8 and 11 are arranged to operate in arepulsive mode. This arrangement is capable of supporting the rotatingring 3 in the axial direction during rotation. FIG. 4 illustrates thedesign of the floating ring 3 in accordance with the preferredembodiment. The ring-spinning system device is assembled together byeight non-ferrous material bolts. FIG. 3 shows the principal ofoperation of the system of the present invention. The permanent magnets2 (FIG. 1), which are arranged on the stator body 1 (FIG. 1) uniformly,are used to generate a fixed magnetic field capable of supporting thefloating ring 3 (FIG. 1) in the Z direction (i.e., the axial directionof the system). The electromagnetic coils 11 are arranged in two sets;one set of 4 coils working in the X direction and the other set workingin the Y direction. Each set includes two groups of coils. Each grouphas two coils arranged on the two sides of the stator body 1 and theflux plates 8 between them.

In FIG. 3, the floating ring 3 is shown displaced a small distance offits central position to the right, or in +X direction. The dotted linesin FIG. 3 represent the magnetic field intensity generated by coils C1,C2 excited in one direction and C3, C4 excited in the other direction.The arrows on that line show the direction of the field. On the otherhand, the permanent magnets 2, which are identified as PM1 and PM2 inFIG. 3 generate two field intensity paths shown as solid lines with thearrows indicating the direction of the field lines. Examining the righthand side air gap, which has a smaller gap than the left side gap, thenet magnetic field intensity is the difference between the fieldgenerated by the permanent magnet and the one generated by the coils. Onthe other side, the net magnetic field intensity is the sum of the twofields. In other words, the magnetic field intensity at the smaller airgap is reduced and the field intensity at the larger air gap isincreased. Therefore, the net restoring force acting on the floatingring will act in the −X direction, i.e. to restore the ring to itscentral position. The same principal works as well in the Y direction.Therefore, by controlling the direction and value of the current passingthrough the coils the ring can be centered.

The modification of the field intensity at the air gap may be referredto as field modulation. The two sets of the electromagnetic coils 11 andtheir flux paths are separated by using two return path plates 12 and 13(FIGS. 1, 7A and 7B), which preferably have about 5 millimeter (mm) airgap between them. This arrangement eliminates, with a great success, thecoupling between the X and Y sets of coils 11.

For full validation of the present invention, a complete finite elementmodel was carried out, as shown in FIG. 11. The real model was enclosedwithin a cylinder of air with a greater diameter than the model by 150%and greater in height by 150%. This was needed to apply far fieldboundary conditions at the surfaces of that cylinder. These boundaryconditions were imposing a tangential flux field at all the boundingsurfaces of that cylinder. FIG. 11 shows the model meshed with aircylinder removed. The total number of elements used to mesh this modelis 370000. This huge number of elements is used in order to obtain themost accurate results. On the other hand, the time taken to perform onerun is about 10 min. This type of analysis has the advantage over theother methods (i.e. closed form solution . . . ) in that there is nosimplification of the model geometry and it takes into consideration anyflux leakage.

The present invention was studied with the floating ring displaced fromthe stator center incrementally 0.25 mm step in the X direction. Anotherstudy was carried out with the floating ring displaced in the Zdirection to get the holding force in the Z direction that will supportthe ring weight and the axial force resulting from the yarn tension. Forthe current configuration, the holding Z force calculated (FIG. 13) isfound to be about 5 [N]. This force is greater than the sum of thefloating ring weight and fiber tension in the Z direction by 5 times.

The materials used to manufacture the different components of thecurrent invention are: the stator body is made of Aluminum or anynon-magnetic material, the flux plates, floating ring and return fluxplate are made of silicon iron, the floating ring spacers, the statorspacers and the axial disk support are made of plastic. The electric andmagnetic properties of all these materials are available in any materialhandbook.

FIG. 12 shows the relation between the restoring force and theexcitation current for 0.25, 0.5, 0.75 mm displacement of the floatingring from its central position. At the point (F0) of intersection withthe current axis the sum of the forces acting on the ring is equal tozero. This does not mean that there is no force holding the ring at thatpoint, but the force holding the ring in the X direction is equal to theforce in the −X direction. So, by increasing the current with a smallamount the ring will start to move in the direction where the air gap islarger. By this action the floating ring win restore its centralposition.

FIGS. 8, 9 and 10 show nonmagnetic spacers and the supporting ring. Asdescribed above, the two spacers are mounted on the floating ring andthe other two are mounted on the stator body facing the other twospacers. The clearance between the facing spacers preferably is designedto be 0.75 mm in order to leave a 0.25 mm as an air gap between thefloating ring and the stator. This 0.25 mm air gap is important in startup of the device. Of course, the present invention is not limited to anyparticular dimensions for the components described herein. However, forthis particular design it has been determined that if this gap is lessthan this value the field modulation will not be able to pull thefloating ring away from the stator. However, inversely, the magneticforce will increase in the direction of closing that gap more. This isquit clear from FIG. 12 at the 0.25 mm gap curve, where it can be seenthat this curve is nearly tangent to zero force at 2.25 ampere (A), andif the current is increased the force starts again to increase in theopposite direction (i.e., trying to close the small gab further).

The supporting disk 7 (support the floating ring in the Z direction)will allow 1 mm for the floating ring 3 to be shifted downwards due toany unexpected disturbance. The permanent magnets 2 will still becapable of lifting the floating ring 3 up again. This action can be seenfrom FIG. 13 at 1 mm displacement where the resultant force in the Zdirection is still about 5 Newton (N).

FIG. 14 shows the feedback control system of the present invention usedto maintain the floating ring in its central position in accordance withthe preferred embodiment. A conventionalproportional-integral-derivative (PID) controller 30 preferably is usedas a core of the control system. The control system 30 uses the twodisplacement sensors 20 (FIG. 2) to sense the floating ring position andfeeds this information back (feedback signal) to the control unit 30.The control unit 30 calculates the difference between the feedbacksignal and the set point value and uses this difference through the PIDalgorithm to generate the required output signals. These signals arethen amplified by amplifiers 31 and 32 and fed to respective differentsets of the electromagnetic coils 11.

It should be noted that while the present invention has been describedwith reference to certain preferred embodiments, the present inventionis not limited to these embodiment. The present invention is not limitedto any particular dimensions for the components or with respect to thematerials used to make the components. Also, the present invention isnot limited to any particular arrangements for the permanent magnets andthe electromagnetic coils. It should also be noted that although thepresent invention has been described with reference to ring-spinning,the present invention is applicable to any area of technology where itis necessary or desirable to suspend some type of device duringoperation, such as a ring or some type of bearing, for example. Othermodifications may be made to the embodiments described herein withoutdeviating from the scope of the present invention.

1. A magnetic elevation system comprising: a stator assembly having apermanent magnet assembly secured thereto, the stator assembly beingsubstantially cylindrical in shape; a support assembly configured tosupport a metallic device that is to be magnetically elevated, thepermanent magnet assembly providing a magnetic force that is exerted onsaid metallic device in at least a first direction; an electromagneticcoil assembly capable of generating a magnetic force that is exerted onsaid metallic device in at least a second direction; and a feedbackcontrol system configured to detect displacement of said metallic devicein at least the first and second directions and to cause the magneticforce being generated by the electromagnetic coil assembly to be variedto correct displacement of said metallic device.
 2. The magneticelevation system of claim 1, wherein the system is a ring-spinningsystem for making yarn, said metallic device being a ring of thering-spinning system, the ring having an eye thereon, and wherein thering spins as it is elevated by the magnetic forces produced by thepermanent magnet assembly and by the electromagnetic coil assembly, thespinning of the ring causing the ring to be displaced from a centerlocation in at least one direction, and wherein the feedback controlsystem causes the magnetic force generated by the electromagnet coilassembly to be varied so as to correct for the displacement while thering is spinning.
 3. The magnetic elevation system of claim 1, whereinthe permanent magnet assembly generates a magnetic force that is exertedon the metallic device in a Z direction and wherein the electromagneticcoil assembly generates a magnetic force that is exerted on the metallicdevice in X and Y directions, the X and Y directions being transverse toeach other and transverse to the Z direction.
 4. The magnetic elevationsystem of claim 3, wherein the feedback control system includes at leasttwo inductive displacement sensors that detect the displacement of themetallic device and generate respective output signals having valuesrelating to amount and direction of displacement of the metallic device.5. The magnetic elevation system of claim 1, wherein the electromagneticcoil assembly comprises two sets of electromagnetic coils, the two setsof electromagnetic coils having the stator assembly and said metallicdevice disposed between them.
 6. The magnetic elevation system of claim5, wherein each set of electromagnetic coils comprises fourelectromagnetic coils.
 7. The magnetic elevation system of claim 1,further comprising a first non-magnetic annular disk disposed on saidmetallic device and a permanent magnet secured to the non-magneticspacer.
 8. The magnetic elevation system of claim 7, further comprisinga second non-magnetic annular disk disposed on the support assembly anda permanent magnetic secured to the second non-magnetic annular disk. 9.The magnetic elevation system of claim 8, further comprising anon-magnetic spacer disposed on said metallic device.
 10. The magneticelevation system of claim 9, further comprising a non-magnetic spacerdisposed on the stator assembly adjacent the non-magnetic spacerdisposed on said metallic device.
 11. The magnetic elevation system ofclaim 5, further comprising first and second flux plates having thestator assembly, said metallic device, the support assembly and theelectromagnetic coil assembly disposed between them.
 12. The magneticelevation system of claim 11, further comprising third and fourth fluxplates having the first and second flux plates, the stator assembly,said metallic device, the support assembly and the electromagnetic coilassembly disposed between them.
 13. A method for magnetically elevatinga metallic device, the method comprising: providing a stator assemblyhaving a permanent magnet assembly secured thereto, the stator assemblybeing substantially cylindrical in shape; supporting a metallic devicethat is to be magnetically elevated on a support assembly, the permanentmagnet assembly providing a magnetic force that is exerted on saidmetallic device in at least a first direction; and generating a magneticforce with an electromagnetic coil assembly that is exerted on saidmetallic device in at least a second direction; and with a feedbackcontrol system, detecting displacement of said metallic device in atleast the first and second directions and causing the magnetic forcebeing generated by the electromagnetic coil assembly to be varied tocorrect displacement of said metallic device.
 14. The method of claim13, wherein the method is a method of making yarn in a ring-spinningsystem, said metallic device being a ring of the ring-spinning system,the ring having an eye thereon, and wherein the ring spins as it iselevated by the magnetic forces produced by the permanent magnetassembly and by the electromagnetic coil assembly, the spinning of thering causing the ring to be displaced from a center location in at leastone direction, and wherein the feedback control system causes themagnetic force generated by the electromagnet coil assembly to be variedso as to correct for the displacement while the ring is spinning. 15.The method of claim 13, wherein the permanent magnet assembly generatesa magnetic force that is exerted on the metallic device in a Z directionand wherein the electromagnetic coil assembly generates a magnetic forcethat is exerted on the metallic device in X and Y directions, the X andY directions being transverse to each other and transverse to the Zdirection.
 16. The method of claim 15, wherein the feedback controlsystem includes at least two inductive displacement sensors that detectthe displacement of the metallic device and generate respective outputsignals having values relating to amount and direction of displacementof the metallic device.
 17. The method of claim 13, wherein theelectromagnetic coil assembly comprises two sets of electromagneticcoils, the two sets of electromagnetic coils having the stator assemblyand said metallic device disposed between them.
 18. The method of claim13, wherein each set of electromagnetic coils comprises fourelectromagnetic coils.
 19. A computer program for controlling adirection and magnitude of a magnetic force being exerted on a metallicdevice being magnetically elevated, the program being embodied on acomputer-readable medium, the program comprising: a first code segmentthat processes output signals from at least one displacement sensorrelating to an amount of displacement of said metallic device in atleast a first direction, the first code segment determining the amountof displacement from the signals output from said at least onedisplacement sensor, and a second code segment that generates controlsignals based on the amount of displacement determined by the first codesegment, the control signals generated by the second code segmentvarying the direction and magnitude of the force being exerted on themetallic device to correct for the displacement of said metallic device.20. The computer program of claim 19, wherein the computer program isimplemented in a ring-spinning system for making yarn, the metallicdevice being a ring of the ring spinning system.